I am involved in a pre-stack seismic inversion project.
I have:
1- Four horizons from the Interpreters, tracking with very high confidence., and
2- RMS velocity field by Processor from a PSTM / PSDM. As you can see in the picture attached, there is no consistency between the time / depth structure and the velocity field.
The area under study has 200 sqkm, Kirchhoff operator was applied to the picked interpretations. Stacking velocity analysis were spaced 500 m, max offset 4667 m, fold 249; I have four wells available with markers defined for each layers.
As you can see in 53.jpeg, the horizons show a high structure between 521 - 553 st, and the velocity field, in color, show low values.
The trend of seismic p-wave velocity is increasing with depth and laterally follwing the same trend. However the structure (Valley/graben/channel) having curvature at st. 521 is also show increasing velocity. The applied Krichoff operator is best in indicating the horozon boundaries.
Try with, interval velocity or Dix velocity model, may work. Increase the sample frequency.
integrate with reflectivity series and synthetic seismogram
Is checkshot data available?
Computations and modeling sometimes depend heavily on certain basic hypotheses, besides interpretational artifacts are a always a possibility In the absence of a plausible logical justification.
You are not the first one to point out differences of this type. The seismic processor looks at velocity panels, the interpreter looks at time/depth sections. The seismic processor should also look at the time/depth sections to avoid obvious discrepancies such as the one you found.
I think you will find that there would be no significant change to the time/depth section if the velocity pick was modified to be more consistent with the interpreted horizons. As a consultant I always interact with the seismic processor (if possible) to avoid situations like this.
Ernest, thanks for your answer. I know that the processor velocities are for optimize the stacking, so the final imaging, and not - necessaary - means the same for geological structure.
In my example, I have not only one 3D, but also a more 3D surveys around it. And, the question is due that, e.g., at west, the velocities follow the horizons. I talking about the same geol-seismic horizons, of course.
Look at the new picture, please, to ilustrate two things that I put emphasis: 1) the are more than one 3D volume, 2) I know that not necessarily the velocities follow the structure, but in this particular case, it inverted, opposite the structure.
From your two pictures I am not certain where (how often) the velocity scans were run. Perhaps you should just reevaluate the velocity scans based upon your horizon picks and use your updated values. That is what I would do in a typical situation. If you encounter significant differences (in delta T due to velocity change) you should reprocess some lines with the corrected velocities.
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